Discussion on the application of temporary wire pulling in power lines

Installing temporary guy wires is a common safety measure in power line construction. Article 6.4.5 of the Electric Power Safety Work Regulations requires that "before tightening or removing the wires, the guy wires, pile anchors and pole towers should be checked. If necessary, the pile anchors should be reinforced or temporary guy wires should be added." The main function of the temporary guy wire is to balance the tension of the overhead line after the conductor is hung on one side, so that the tension pole remains balanced and stable when tightening the wire.

With the rapid development of Yibin power grid, many transmission lines, urban distribution networks and rural distribution lines are undergoing infrastructure construction, overhaul and technical transformation. It is inevitable to carry out power line erection, replacement of overhead lines and replacement of old poles and towers. At this time, if some on-site safety technicians are lax in safety management, the construction team is not aware of the safety technical measures for setting temporary pull lines, and there is a phenomenon of not setting temporary pull lines or incorrect temporary pull lines when tightening, withdrawing and replacing tension poles and towers. Many safety hazards will be buried, and poles may fall or break, and in serious cases, personal injury and death accidents may occur.

At present, the overhaul and technical transformation of old transmission lines and the upgrading of rural distribution lines of Yibin Electric Power Bureau are being carried out in an intense and orderly manner. Due to the large number of line engineering projects and the wide range of areas, it was found during the safety inspection of the construction site that some construction teams did not have enough understanding of the safety technical measures for setting up temporary pull lines. When tightening or removing lines, there was a phenomenon of not setting up temporary pull lines or setting up temporary pull lines incorrectly. How can we achieve the standardization and standardization of temporary pull lines in line construction operations to ensure the safety of line construction operations? The following is a brief discussion on the use occasions, production requirements, and composition of the temporary pull lines of Yibin Electric Power Bureau.

1 Application occasions and production requirements of temporary line pulling

1.1 Before replacing the guy wires of the operating line tower, temporary guy wires need to be installed in the same position as the permanent guy wires to be replaced.

Temporary guy wires can be fixed on the original guy wire rods, but the original guy wire rods must be excavated and inspected. The excavation depth should not be less than 300mm, and the degree of rust on the guy wire rods should be less than 4mm before they can be used.

If the original guy wire rod is not used, a temporary guy wire must be fixed with a ground anchor or iron stake. The angle between the wire rope and the ground should not be greater than the angle between the original guy wire and the ground, and should not be greater than 45°.

1.2 Before replacing the guy wire rod, it is necessary to install a temporary guy wire in the direction of the replacement guy wire rod using ground anchors or iron stakes. The angle between the temporary guy wire and the ground should not be greater than the angle between the original guy wire and the ground.

1.3 Before the pole tower is newly built, temporary iron piles are needed to fix the capstan, guide pulley, wire pressing pulley and traction pulley assembly; before the permanent guy wire of the pole tower is assembled, temporary guy wire is needed to fix the pole tower.

1.4 Before replacing and deploying the line conductor and ground wire, in order to protect the tower conductor, ground wire crossarm and tower body from deformation due to unbalanced force, it is necessary to use temporary guy wires to fix the tower. Each overhead line (conductor, ground wire) must be equipped with a temporary guy wire on the extension line in the opposite direction of the tightening line. At this time, the temporary guy wire should be installed at the stress point of the tower conductor, ground wire crossarm and tower body. Under the condition of not affecting the hanging line, the fixed position should be as close to the hanging point as possible, generally 20cm to 30cm away from the conductor hanging point. For the 10kV single-pole medium-phase conductor, the temporary guy wire should be hit on the main pole at the lower end of the top iron clamp.

1.5 Before using the pole to assemble the tower or lift heavy objects, it is necessary to install temporary guy wires to fix the pole. When using the pole to assemble the tower or lift heavy objects, the temporary guy wires are stressed and play a role in stabilizing the pole.

2 Composition of temporary wire pulling system

Since August 2006, Yibin Electric Power Bureau has implemented standardized management of temporary wire pulling tools. Through many designs and discussions, it has manufactured temporary wire pulling tools suitable for on-site operations. It has also conducted multiple on-site tensile tests to verify that the designed temporary wire pulling combination tools are safe and reliable, while also being convenient and efficient for on-site construction operations.

The temporary wire pulling system consists of five parts: temporary anchor piles, wire rods, wire ropes, fixing hardware and wire tensioning adjustment tools.

2.1 Pit anchor refers to a horizontal anchor buried in a pit. Considering safety and specifications, Yibin Electric Power Bureau uniformly chooses to use steel anchors. In order to make more effective use of the bearing surface of the anchor, the shape of the anchor is updated from the traditional cylinder to a rectangular parallelepiped. The specifications of the steel anchor are: 800mm in length, 300mm in width, and 8mm in steel plate thickness.

When using pit anchors, a "horse path" should be excavated in the direction of the pit anchor pull rod, and the force direction of the "horse path" should be consistent with that of the temporary pull wire.

Yibin Electric Power Bureau conducted a large number of tensile tests on square anchors and found that under different soil conditions, when the burial depth is 1.0~1.5m, the inclined tensile force that can be withstood is 1.04-11.57t. The calculation of the allowable inclined tensile force of the anchor is shown in the following table:

2.2 Iron piles are made of round steel, with one end forged into a pointed head and the other end being a flat head for hammering. In actual work, according to the number of iron piles, they are divided into single iron piles and multiple iron piles. At present, the line construction of Yibin Electric Power Bureau all adopts "plum blossom iron piles", which are composed of one main pile and two auxiliary piles.

When setting up iron piles, according to the force direction, the iron piles should be tilted 15° to 30° in the opposite direction of the force, and hammered into the ground obliquely with a sledgehammer. After hammering in, check whether the iron piles are firmly embedded. The distance between the iron piles and the tower should ensure that the angle between the temporary tension wire and the ground is 30° to 45°, and the depth of the iron piles is about 2/3 of the length of the iron piles.